Continuous techniques for making flat woven synthetic fabrics



March 31, 1970 RT ET AL 3,503,106

CONTINUOUS TECHNIQUES FOR MAKING FLAT WOVEN SYNTHETIC FABRICS Filed June2'7, 1968 llo Ti/5.4..

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Sr/eETcm/ve mm 09/64 122) lz/ea 54/276 NECAW/V/SM INVENTORS fi Pro/Y OP7- BY M410 Z. Seawrz ATTOPAEJ/ United States Patent US. CI. 28-72Claims ABSTRACT OF THE DISCLOSURE A continuous technique formanufacturing flat woven fabrics wherein thermoplastic material isextruded into a web which is stretch-oriented to increase its tensilestrength, the web being slit before or after orientation to produceindividual strips that are folded into narrow ribbons in which the cutedges of the strips are concealed, the ribbons being directly suppliedinto a loom where they are woven into a fiat fabric.

RELATED APPLICATION This application is a continuation-in-part of ourapplication Ser. No. 378,179, filed June 26, 1964, now Patent 3,398,220.

This invention relates generally to a technique for making a fiatfabric, and more particularly to a continuous process wherein a web ofsynthetic material is converted into ribbon-like yarns which aresupplied directly into a weaving loom to produce a flat fabric.

Many uses exist for flat fabrics formed by interwoven ribbons ofsynthetic plastic material, such as polypropylene. Such woven fiatfabrics serve, for example, as primary backings for tufted rugs in whichpile yarns are needled into the backing. These sheet-like fabrics arealso widely used for plastic bags and bales. When laminated to a thinfilm, a reinforced light-weight material is produced havingexceptionally high tensile and tear strength, this material being usefulfor tarpaulins and for many other purposes.

The conventional technique for producing ribbon-like, synthetic yarns tobe Woven into a flat fabric involves extruding the synthetic materialinto a web which is oriented and slit into individual ribbons. Theseribbons are then Wound on a beam for use as warp yarns or onto suitablepackages for use as filling yarns. In weaving operations, the ribbonyarns are thereafter unwound from the beam and the packages. Henceexisting techniques involve discontinuous winding and unwindingoperations, as well as transfer operations which add materially to theover-all cost of production.

Another drawback to existing techniques is that in slitting an orientedweb to produce ribbons of yarn size, the slitting action tends toroughen or fibrillate the edges of the ribbon, as a consequence of whichthe edges are not smooth but exhibit fine fibrils. In weaving, suchfibrils tend to interfere with the proper functioning of the loom andmay result in a break-down, particularly in high speed weavingoperations.

Accordingly, it is the main object of this invention to provide a noveltechnique for continuously producing flat fabric by converting a web ofsynthetic material into strips which are folded into narrow ribbons, theribbons being directly woven into a fiat fabric.

A significant feature of the invention is that it eliminates suchconventional operations as packaging and 3,503,106 Patented Mar. 31,1970 p CC beaming, thereby effecting significant production economies.

Another object of the invention is to provide a continuous technique ofthe above type in which the folding serves to conceal the cut edges ofthe strips, thereby facilitating proper weaving operations, the foldingserving to improve the edge tear-strength and hence the tear values ofthe resultant fabric.

Also an object of the invention is to provide a low-cost, sheet-likewoven fabric whose structural characteristics are superior to thoseheretofore produced at higher cost.

Briefly stated, these objects are attained in a technique wherein moltenthermoplastic material, such as polypropylene, is continuously extrudedinto a film-like web which is stretch-oriented to increase its tensilestrength, the web being slit before or after orientation to produceindividual strips which are then folded with the cut edges thereofturned inwardly to provide relatively narrow ribbons having smoothfolded edges, which ribbons are fed directly into a loom where they areinterwoven to form a flat fabric. Thus the process'in accordance withthe invention transforms molten raw material into a woven fabric in arapid, uninterrupted, sequential operation.

For a better undestanding of the invention, as well as other objects andfurther features thereof, reference is made to the following detaileddescription to be read in conjunction with the accompanying drawing,wherein:

FIG. 1 schematically shows a system for carrying out a continuoustechnique for producing a sheet-like woven fabric in accordance with theinvention;

FIG. 2 is a perspective view of one of the folding units;

FIG. 3 is a side view of the folding unit and of the associated calenderrolls.

FIG. 4 is a transverse section taken through a ribbon produced byfolding a strip; and

FIG. 5 is a plan view of the sheet-like fabric produced by the weavingoperation.

The raw material used to make fabric in accordance with the inventionmay be any known form of molecularly orientatable, thermoplasticpolymeric material such as polyethylene, polypropylene, polyamide,polyester. Polymers are synthetic substances composed of large moleculesthat have been formed by the union of a group of single molecules withone another.

As shown in FIG. 1, the selected raw material is rendered molten andextruded through a suitable extruder assembly 10 to form a film-like web11. The manner in which the raw material is converted into Web-form isentirely conventional, and any standard equipment may be used for thispurpose.

Web 11 is pulled from extruder 10- by feed rolls 12, the Web beingcooled before it reaches these rolls, so that it is below its softeningpoint. Longitudinal orientation is then effected by the process ofdrawing to irreversibly stretch the web and thereby increase its tensilestrength considerably. This is accomplished by cooled draw rolls 13, theperipheral speed of which is greater than that of heated feed rolls 12,the ratio between the two rolls being termed the draw ratio.

The stretch-oriented web 14 emerging from draw rolls 13 is conveyed intoa slitter mechanism 15 Where it is divided by rotary blades orequivalent means into a multiplicity of individual flat strips S to SAlternatively, slitting may be effected prior to orientation. Becauseorientation imparts to the material a tendency to fibrillate at theedges when subjected to stresses, strips S to S emerging from theslitter have somewhat rough edges containing fine fibrils.

Each strip is conveyed through a folding unit (F to P which, as shownseparately in FIG. 2, may take the form of a conical sleeve 16 having atapered bore 17 therein with an oblong cross-section of progressivelydiminishing dimensions. Thus the edges E and E, of Strip S entering theinput side of the folding unit at which the bore has its largestdimension, engage the wall of the bore and are caused thereby to foldover as the bore dimensions become smaller, so that the strip emergesfrom the output side of the bore with the edges E and E, folded over, asshown in FIG. 4.

The folded-over edges are pressed down by calender rolls 18, as shownseparately in FIG. 3, to form fiat and relatively narrow ribbons R andR,,, the creased edges of the ribbons being the folded-over edges of thestrip. Hence the creased edges of the ribbon present a smooth surface.The width of the strip is such that when folded over as described above,the resultant ribbon constitutes a yarn of the desired denier.

Ribbons R to R are then fed into a standard loom 19 for weaving man-madeyarns, such a a Draper loom, the ribbons being interwoven to form afabric having a flat surface, as shown in FIG. 5. In practice, where itis desired that the fiat yarn have, say, a two-mil thickness, the stripsare made in a one-mil thickness to produce folded-over ribbons or flatyarn of two-mil thickness.

It is also possible to carry out the process in accordance with theinvention by commencing with a commercial roll of oriented or unorientedsynthetic thermoplastic material. Where the roll is formed of orientedfilm, the web thereof, as it is unwound from the roll, is fed into theslitter, the resultant strips being first folded and then fed directlyinto the loom in the manner previously described. But should the web beof nnoriented film, the orientation may be etfected in the course offeeding the folded ribbons into the loom by means of stretch rolls. Ineither case, the strips are so folded as to present smooth edges tofacilitate weaving.

While there has been described and shown preferred techniques inaccordance with the invention, it will be appreciated that many changesand modifications may be made therein without, however, departing fromthe essential spirit of the invention as defined in the annexed claims.

What we claim is:

1. A continuous technique for producing a flat fabric, comprising thesteps of:

(a) extruding raw material formed of an orientatable syntheticthermoplastic material selected from the class consisting ofpolypropylene and polyethylene into a film-like web,

(b) orienting the web to increase the tensile strength of the materialto a point at which fibrils are formed at the edgesof individual stripssubsequently derived from the web by slitting,

(c) slitting the web into individual strips,

(d) folding each strip with its fibrillated edges folded in to producerelatively narrow ribbons and then calendering the ribbons to press inthe folds thereof to produce yarn-like ribbons having smooth creasededges; and

(e) interweaving said yarn-like ribbons directly into a flat fabric.

2. A technique as set forth in claim 1, wherein said slitting iseffected before orientation.

3. A technique as set forth in claim 1, wherein said slitting iseifected after orientation.

References Cited UNITED STATES PATENTS 2,960,725 11/ 1960 Lefevre.2,985,503 5/1961 Becker 264-147 X 3,110,905 11/1963 Rhodes 139-420 X3,193,904 7/1965 Evans et al. 57-31 X 3,253,072 5/1966 Scragg et a1.264147 3,327,468 6/1967 Page 57140 3,336,645 8/1967 Mirsky 13911 X3,398,220 8/1968 Port et a1. 264147 3,439,865 4/1969 Port et a1.1'393'89 X FOREIGN PATENTS 180,540 12/ 1954 Austria. 702,381 1/ 1965Canada.

12,462 of 1913 Great Britain. 1,035,227 7/1966 Great Britain.

98,780 10/1961 Norway.

JAMES KEE CHI, Primary Examiner US. Cl. X.R.

